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Control Data Electronic Calculator "Terminal"

Advertisement for Control Data Corporation "Calculator Terminal" for remote connection to CDC's Model 6600 "Supercomputer", November, 1965.

This device wasn't truly a calculator. It was essentially a keyboard, display, and data communications device that connected via acoustic coupler to a large timeshared Control Data supercomputer, to allow complex mathematical operations to be performed with the familiar user-intreface of an electronic calculator, in the days when electronic calculators were in their infancy.

This device, while not completely unique in theory, was definitely unique within its timeframe. Later, calculator companies such as Mathatronics, Wang Laboratories, and Computer Design Corporation (A.K.A. Compucorp) developed means by which a calculator could be "remotely accessed", sometimes by a single user, or a number of users (typically no more than 32 simultaneous users) over a dial-up modem or dedicated data circuit connection. With a properly configured CDC 6600 computer, up to 2000 of these "calculator terminals" could operate from one mainframe.

This device provided a familiar and easy-to-use interface for scientists, statisticians, and business people who didn't want to fuss with learning programming languages, and "waiting" for computer time. The machine was essentially the equivalent of a "smart terminal", which would send commands entered by the user on the keyboard to the mainframe computer, which ran a special executive program that performed the math operations of the calculator. The results of operations were then transmitted back to the calculator terminal for display on the projection-style display.

Because the high-level math functions were performed by the executive process running on the mainframe, extremely complex math operations could be performed with just a few keypresses on the calculator terminal.

The idea was a good one, but it came at a cost. The terminals were big, heavy, and expensive. You needed a phone line to allow it to connect to the remote data center, and you paid a monthly fee to use the computing services of the mainframe. While it was certainly cheaper than renting time on a general-purpose timeshared computing service, it was still a a rather expensive proposition.

Control Data took out US Patent number 3388031 on this device. The patent goes into substantial detail on the design and operational aspects of this specialized data terminal.

If you have one of these old "calculator terminals" laying around gathering dust (they are pretty useless today, as there aren't many operating Control Data 6600 systems running anymore, not to mention there's no clue as to whether the executive code that provided the services to the "terminals" even exists anymore), or if you ever used one of these things, I'd love to hear from you. Please click the EMail link at the top of this page to send me a message.